1. Field of the Invention
This invention concerns supplying power to devices which utilize an AC to DC power supply or power adapter.
2. Related Art
On Jul. 31, 2001 the President of the United State issued the executive order, Energy Efficient Standby Power Devices. This executive order required that government agencies purchase equipment whose standby power is less then one Watt when possible. Australia is participating in the International Energy Agency""s one Watt Program. The International Energy Agency has had three international workshops on standby power. Philips has programs, GreenChipTM and STARplugTM, that aim to reduce standby power and increase efficiency in power converters. ON Semiconductor has controllers for designing efficient wall adapters. This shows progress on making new devices with increased efficiency and reduced standby power, but legacy devices will continue to waste power until they have been phased out over a period of many years.
It should therefore be appreciated that the need exists to reduce standby power in existing devices.
The foregoing need is addressed in the present invention. According to a method form of the invention, power consumption is reduced for power supplied by a voltage adapter, such as an AC/DC adapter, an AC/AC adapter, a DC/DC adapter or a DC/AC adapter. (A voltage adapter is also referred to sometimes as a voltage xe2x80x9cconverter.xe2x80x9d) In a first step, a power source is connected to a power unit, including the voltage adapter and control circuitry. The voltage adapter supplies power to a load, such as a computer system. A load current supplied by the voltage adapter and an output voltage of the voltage adapter are measured by the control circuitry, and a control device of the control circuitry selectively disconnects the voltage adapter from the power source. The disconnecting is responsive to the control circuitry inferring from the measured current and voltage that the load is low, i.e., turned off, or at least operating in a reduced power consumption mode. (In this context the term, xe2x80x9cturned offxe2x80x9d is meant to include the load being disconnected from the power unit.)
In another aspect, the control circuitry infers that the load is low by comparing the output voltage and current to respective threshold values.
In a still further aspect, the load is considered to be low if the output voltage is high (also referred to herein as a xe2x80x9cnormalxe2x80x9d output voltage) and the load current is low. This circumstance indicates that the power unit is turned on, but the load is drawing less power than it does in normal operation. For example, the device drawing the load may be in a sleep mode, or it may be turned off. In this circumstance, disconnecting the supply line from the voltage adapter reduces leakage power in the adapter.
In yet another aspect, the disconnecting is responsive to the control circuitry inferring that load is drawing more power than is desirable (referred to herein as an xe2x80x9coverloadxe2x80x9d). This is inferred from a high load current and a low output voltage. For example, a computer system load may have a malfunctioning battery, or there may be a short circuit on the output of the voltage adapter. In this circumstance, disconnecting the supply line protects the adapter from overload.
Objects, advantages, additional aspects and other forms of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings.